ci: Tag image with `latest` tag and publish it

.gitlab-ci.yml

@@ -17,6 +17,8 @@ build_image:
     - docker login -u "gitlab-ci-token" -p "$CI_JOB_TOKEN" $CI_REGISTRY
     - docker build --pull -t "$CI_REGISTRY_IMAGE:$CI_COMMIT_TAG" .
     - docker push "$CI_REGISTRY_IMAGE:$CI_COMMIT_TAG"
+    - docker tag "$CI_REGISTRY_IMAGE:$CI_COMMIT_TAG" "$CI_REGISTRY_IMAGE:latest"
+    - docker push "$CI_REGISTRY_IMAGE:latest"
   only:
     - tags
   tags: